Radiant energy relay means



May 31, 1960 .1. H. GuYToN RADIANT ENERGY RELAY MEANS RYE Filed Oct. 22, 1956 V Claims. (Cl. 317-147) Ind., assignor to General Detroit, Mich., a corporation of This invention relates to radiant energy relay means and more particularly to electronic relay switching means operablevfrom a transmitted radiated signal.

Electronically controlled relay means currently are in considerable demand for operating various devices at a` distance without interconnecting wires. As illustrative only'of such a use, is that of providing equipment for automatically raising or lowering garage doors controlled from a transmitting unit mounted in an automobile at a distance from the door.

It isan object in making this invention to provide eleci tronically controlled relay switching means operable from a radiated signal to actuate desired apparatus.

, It is a further object in making this invention `to provide radiant energy actuated relay switching means for operation of desired apparatus from a distance operable in the low frequency spectrum by continuous unmodulated waves.

It is a further object in making this invention to provide relay switching means actuated by low frequency continuous unmodulated waves and having a sharp selectivity and using coded frequencies.

It is a further object in making this invention to cause the relay switching means to ignore signals of proper frequency which are modulated in amplitude.

With these and other objects in view which will be apparent as the specification proceeds, my invention will be best understood by reference to the'following specification and claims and the illustration of the accompanying drawing, in which:

-Figure 1 is a circuit diagram of a radiant energy operated electronic switching means embodying my invention.

Figure 2 is a graph of the wave form of the unmodulated operating signal; and

Figure 3 is a graph of the wave form of a modulated noise signal that the system will reject.

LIn radiant energy operated remote switching means, various sources of radiant energy may be used as the operating signal. In the illustration of automatic garage door operation, the automobile utilizing the garage space is equipped with a transmitter for emitting waves of a given signal frequency. When the driver approaches the garage, he closes a switch energizing the transmitter for sending out waves. The electronic relay switching means disclosed herein will pick up this radiant energy and actuate a relay controlling the motor to raise and lower the garage door. The relay will remain actuated in the present instance only so long as the transmitter is energized and will be deenergized to stop the motor when the transmitter is cut off.

In the present illustrative structure it is proposed to operate in the VLF (very low frequency) band. That includes the band from 5,000 to 10,000 cycles. My invention, however, is applicable'to other and higher frequency operation as well and should therefore not be limited in` any way to low frequency operation. In supplying electronic relay switching means for such a use as garage door ice -that adjacent installations will not interfere with each other. In the present case this is done by providing transmitters that aregadjusted to operate at certain spaced definite frequencies to cooperate ywith receivers likewise adjusted to operate on only that frequency and not adjacent frequencies. In Ithe band from 5,000 to 10,000v cycles there is adequate room for dilerent operating frequencies so that neighboring installations will not interfere with each other. Each receiver therefore must have a sharp response characteristic at the desired frequency to which it is adjusted or designed and be substantially unresponsive to adjacent frequency waves.

Referring now more specifically to the drawing, there is shown therein an electronic actuated relay switching means for controlling a remote power switch such as that I associated with a garage door opener. The electronic system includes two stages of amplification comprising the first two tubes T-l and T-Z, the output of the second tube feeding into a coupling transformer which provides the frequency selectivity characteristics and in turn supplies its output to a triggering tube T-4 which controls the relay switching means 2. The relay switching means 2 is connected through suitable wiring to a relay at a remote location for power switching. The tube T-3 located between T-2 and T-4 is utilized as a rectifier and the triode portion for a special service to be described.

A receiving antenna coil 4 is utilized which consists of a ferrite stick indicated by the dash lines around which is wound a coil 4, which antenna is located at a suitable point in the garage `such as over the door to receive a maximum amount of power from the signals. An adjustable condenser 6 is connected across the coil 4 to complete the antenna circuit. One terminal 7 of the antenna circuit is connected directly through coupling'condenser 8 to the control grid 10 of the tube T-1 to apply the incoming signal to the rst amplifying stage. The other terminal of the antenna circuit is grounded. A resistor 12 is connected between the grid 10 and the automatic gain control line 14. Condenser 16 is connected between line 14 and ground.

The plate 18 of the tube T-l is connected through limiting resistor 20 to power supply line 22 to apply plate voltage. Cathode 24 is connected to ground through biasing resistor 26 shunted by condenser 28. The suppresser grid 30 of the tube is connected directly to the cathode 24. The screen grid 32 of tube T-1 is connected through filter resistance 34 to screen grid 36 of tube T-2. Filter condenser 38 is connected between grid 32 and ground and a similar filter condenser 40 is connected beitween grid 36 and ground. A further supply line 42 is connected to grids 32 and 36 through resistance 44. The plate 18 of the tube T-l is connected to control grid 46 0f tube T-2 through coupling condenser 48. This applies the output of the iirst amplifier stage to the second. The suppressor grid 50 of the tube T-2 is connected directly to cathode 52 and thence through biasing resistor 54 to ground. A bypass condenser 56 is connected across resistance 54.

The automatic gain control line 14 is connected through resistor 58 to line 60 and thence through a similar resistor 62 to one terminal of the secondary 64 of the coupling transformer 66 connected in the output of the tube T-2. A resistor 68 is connected between grid 46-and the automatic gain control line 60. Filter condenser 70 is connected between line 60 and ground and together with the condenser 16 and resistances 58 and 62 determines the time constant of the automatic gain control circuit.

The plate 72 of the tube T-Z is connected to the center tap 74 of the primary 76 of the transformer 66, thus irnpressing the output of the tube T-2 on the primary. A condenser 78 is connected directly across the primary 76 Patented May 3l, 1960 and tunes the same to the desired operating frequency of the system. One terminal of the primary 76 is connected to the power supply line 22 through tie line 80. The other terminal of the primary 76 is connected through a coupling condenser 82 with one terminal of the secondary 64 and likewise through coupling condenser 84 to one diode anode 86 of the tube T-3. Diode anode 86 is likewise connected to ground through a biasing resistor 88. A further resistor 90 is connected between the lower terminal of the secondary 64 and the diode anode 86. Condenser 92 is connected across the secondary 64 and tunes the secondary to the same frequency at the primary, and which of course is the operating frequency of the device. A time constant condenser 94 is connected between the lower end of the secondary 64 and ground. The transformer windings are all enclosed in a shielded container which is grounded.

v remaining terminal of the secondary 186 is connected The triggering signal for operating the control relay 2 consists of two composite parts both provided by the transformer 66. These two parts are provided by the primary and secondary windings respectively and when combined provide a sulhciently positive voltage on the control grid 96 of the second section of the tube T-4 to actuate the relay. The operating portion of the signal is that provided by the secondary winding and this signal is developed across the resistance 98 connected between the cathode 100 of the first section of the tube T-4 and ground. A bypass condenser 102 is connected across resistance 98. rl`he output of the secondary is connected directly through line 104 to the control grid 106 of the first triode section and the plate current rectification which occurs develops an actuating voltage across the resistance 98 between `cathode 100 and ground. Through a cathode follower connection this voltage is applied to the control grid 96 of the second section through line 108 and a series resistance 110. A condenser 112 is connected between line S and ground to provide a time constant operation to be described. Thus, when the voltage across resistance 98 reaches a certain predetermined level, grid 96 becomes suliiciently positive to cause suicient electronic flow from cathode 114 of the second section of tube T-4 to plate 116 of this section to actuate the relay.

Operating coil 118 of the relay 2 is connected to plate 116 and also to line 120 which extends to the power supply. The lower stationary contact 122 of the relay 2 is connected through line 124 to one contact 126 of a coupling plug 128 for connection to the motor operator. The movable armature 130 of the relay 2 is grounded. The upper stationary contact 132 is connected through l r' line 134 to a time constant circuit consisting of a series condenser 136 and two resistances 138 and 140 connected to opposite sides of the condenser. Resistance 138 is likewise connected to power supply line 120 but the remaining terminal of resistor 140 is grounded. The remote terminal of condenser 136 is connected directly through line 142 to the grid 144 of the triode section of the tube T-3. The cathode 146 of this tube is connected directly to ground through a variable biasing resistor 148 bypassed by condenser 150. Cathode 146 is likewise connected through resistor 152 to one of the power supply lines 154. The plate 156 of the tube T-3 is connected through line 158 to the plate 116 of the tube T-4 and to one terminal of the operating coil 118 of the relay 2. A condenser 160 is connected directly across the operating coil 118 of the relay 2. Cathode 114 of the second section of the tube T-4 is connected to ground through a variable resistance 162, and also through two resistances 164 and 166 in parallel to tie line 168 extending to power line 154. Plate 170 of the rst triode section of the tube T-4 is connected directly to power line 22 in order to assist the electron llow in the first section.

The power supply section includes two input lines 172 and 174 that are connected to the coupling plug 128, and of course are adapted to be coupled to conventional electrical power such as 115 v. 60 cycles alternating current.

through a voltage doubler section including rectifiers 188 and 190 to power supply line 120. A filter system including resistor 192 together with two condensers 194 and 196 connected to ground on each end thereof, is connected between the voltage doubler section and power supply line 22 to supply filtered power to that line. Therefore power supply line 120 carries unfiltered power whereas line 22, filtered.

In the operation of this electronic switching system it is important that the receiver only operate on signals of the prescribed frequency and does not operate on adjacent frequency signals or various other impulses or noise. Where these devices may be used, there are usually in the vicinity, various other electrical switches such as light switches, motor and other electrical equipment which may create sparking or some pronounced hum. The antenna 4 therefore might pick up these various noise signals and it is essential that such signals do not produce an operation of the relay 2. Tihe amplifier section T-1 is a broad band amplifier which has a flat response over a considerable frequency spectrum say, for example, in the present instance, between 3,000 and 15,000 cycles. The low frequency signals are attenuated by the screen and cathode condenser 28. The next stage including tube T-2, together with the transformer in the plate circuit, establishes the selectivity frequency response. Both the primary and secondary circuits of the transformer 66 are tuned to the desired frequency. Both primary and secondary have similar Q characteristics and are critically coupled through condenser 82.

The actuating signal for triggering the relay is obtained from the secondary and rectied by the grid 106 and cathode 100 of the first section of the tube T-4. This rectified voltage is developed across resistance 98 and applied to grid 96 through coupling resistor 110. When this voltage reaches a predetermined point the second section conducts a sullcient amount of current to permit the coil 118 to pull down its armature 130 against the spring action of spring 198. When the armature 130 is moved down into contact with lower contact 122, a circuit is completed through line 124 to the coupling block 128 to complete an energizing circuit for the remote power relay at the actuator and the garage door is then driven. However, in order to provide a very narrow operating band and to make the device sufciently selective so that it will not operate on closely adjacent frequencies, a restraining voltage is applied to the system. This restraining voltage is obtained from the primary circuit which is connected through coupling condenser 84 to the diode anode 86 of the diode section of the tube T-3. Cathode 146 of the diode is continuously biased by the bleeder network 148--152 and so the diode 86-146 will not conduct, as the signal on the primary increases, until suicient voltage has been developed on grid 96 of the tube T-4 to operate the relay. When this amount of signal voltage has been applied and the relay operates, diode 86-146 conducts and this develops a negative voltage across the resistance 88. This voltage is introduced through resistor and condenser 94 to grid 106 of the rst section of the tube T-4 and is so poled as to prevent' or restrain the development of any more voltage on the cathode as the signal in the input to the amplilier further increases. Therefore, with proper adjustment, the receiver will not develop any more low voltage signal across resistor 98 or that on Vgrid 96 than is just suiiicient to'close the relay, regardless of the input signal strength.

The frequency response of the transformer primary is of course broader than the secondary and therefore the restraining voltage is developed overr a broader band. Any deviation of the incoming signal from the specific designed frequency will therefore decrease the operating voltage on grid 96 faster than the restraining voltage. This results in a sharp relay current cutoff as the receiver signal deviates from its intended frequency, regardless of the' signal strength, and therefore provides the desired selectivity.

The Yvarious time constant circuits of this system are provided 'so-that the relay will ignore any appreciable modulation of the actuated signal and thus cut out the majority of random noise operation. These time constant circuits include the automatic gain control system which biases olf the amplifier so that the vtube T-2 will not be operative to produce an unmodulated Wave output when a modulated wave is received, since, as before mentioned, this systemis intended to be operative only on a continuous unmodulated signal. Therefore the time constantsof the AGC including condensers 16, 70 and resistor 58provide this operation. The operating voltage time constant circuit consisting of resistance 98 and condenser 102 in the circuit lof the cathode 100 are fast compared Vto 60 cycle frequency and produce an average value of operating voltage. The filter 110 and 11-2 in this latter circuit and 160 across the relay provide a sufficient delay to prevent the relay from operating on short noise bursts before the restraining and AGC voltages have had a time to act to explore whether the signal is continuous unmodulated or modulated. This is due to the fact that there is a linite charging time for condensers 84, 16 and 70, although they are intended to act as fast as possible.

In order to explain more in detail how the subject system rejects noise signals and operates only on unmodulated carrier signals, reference is made specifically to Figures 2 and 3. As previously explained, this system develops two voltages, an operating and a restraining voltage. The operating Yvoltage is determined by the average value of the signal applied to the antenna. The restraining voltage, on the other hand, is determined by the modulation peak of the signal applied. Fig. 2 illustrates a continuous unmodulated carrier signal for operating the relay. Since this signal is unmodulated, the peak value of the carrier wave is equal to the average value. Therefore the operating and restraining voltages in this instance are determined by signals of the same amplitude. As the unmodulated signal applied to the grid 106 is increased to a point just beyond the operating value, the voltage across resistor 98 will cause operation of the relay 2. At slightly above this operating point, a restraining voltage is provided which is rectilied by the diode 86-146. This voltage appears across resistor 88. A ny further increase in the input signal causes equal increases in the operating and restraining voltages across resistors 98 and 88 respectively, which are so poled as to cancel and therefore the resultant operating voltage remains at this Value. The polarity opposition of these two voltages can be easily seen from the circuit diagram Fig. l. Thus a continuous signal produces a suicient voltage to produce relay operation at any input above threshold.

Random noise, however, should not operate the relay system and such noise has been found to contain modulation. An illustrative wave from a noise signal is shown in Fig. 3. In that instance it will be noted that the peak Value of the high frequency carrier wave as shown by hne P is higher than the average value of the modulated wave as shown by line N. This modulated noise signal may appear at the output of T-Z when the antenna receives anoise signal. In the design of this equipment the time constants-of Vcondensers 84 and 94 with their associated resistors 88 and 90 were made long compared t tite modulation envelope as shown in Fig. 3. Condenser 84 may charge very rapidly when a peak X in the modulation curve is reached. However, the leakage path for condenser 84 which includes resistor 88 requires a substantial time for discharge so that the voltage on condenser 84 remains high under these circumstances until such time as another peak X appears to slightly recharge the condenser 84 to its original value. This voltage is the restraining voltage as above described. At the same time the operating voltage tending to cause relay operation which appears across resistor 98 may rise and fall with the modulation of the carrier signal and it is the average value of this fluctuating voltage that produces the operating voltage. This average value of the operating voltage will be less than suiicient to cause relay operation because of the disproportionately large amount of restraining voltage developed in the presence of modulation. Under these conditions therefore, noise signals will not erroneously operate the relay. The time constants of resistor and condenser 112 and condenser 160` and relay coil 118 are sufficiently long to prevent relay operation during the application of such a modulated peak wave as that shown in Fig. 3.

The function of the triode section of tube T-3 is to prevent cycling or chattering of the control equipment. For example, when a control signal is received, and relay 2 closes, this will further actuate the power relay and start the motor. Thus several switches are closed and a motor begins to run. This causes a sudden outburst of contact sparks and brush sparking in the immediate vicinity. These noise signals are immediately applied to the antenna input and the receiver, since it recognizes noise Waves which it is designed to ignore, would tend to drop out the relay. If the relay opened, ithe operating signal would be again applied and that transmitted through and again cause relay operation which would result in the same noise signal. Some means must therefore be provided to hold the relay 2 in long enough to have the noise of the switches and of the motor-starting dissipate. This is the function of the triode section of the tube T-3. This tube is normally biased to cut off through resistor 140, however, it is noticed that when the relay 2 closes on its lower contact, it opens the circuit through the back contact 132, ungrounding the upper end of resistor 138. Current may now ilow through resistor 138 from the power line 120 to charge lthe condenser 136. This produces a positive voltage at the upper end of resistor 140 which is connected directly to the control grid 144 and tube T-3 may now conduct. This only, of course, applies for a predetermined short period depending on the charging time of the condenser 136 but during this time the triode section of tube T-3 can conduct suiciently to maintain current flow through relay coil 118 and keep the armature attracted to overcome this burst of noise at starting. Thereafter the relay is held down by the normal signal.

=It is therefore evident from the above that an electronic radiant energy actuated system is herein provided which requires a minimum of simple tuned circuits and which is veryselective to frequency of a continuous unmodulated signal and will retain the switching means actuated as long as the signal is present and will not be actuated by noise and extraneous waves.

I claim:

1. In control means, a source of electrical power, amplifying means connected to said source of power selective to only a narrow frequency band, means for applying a signal to said amplifying means, relay switching means connected to said source of power, electronic means connected in circuit with said relay switching means to control the operation of the same, means interconnecting the amplifying means and the electronic means to apply an actuating signal to the latter from the amplifying means and a second interconnecting means I? between the amplifying means and the electronic means to apply a restraining signal to thefelectronic means when the actuating signal has exceeded a value causing operation of the relay switching means.

2. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, signal receiving' means connected to the source of power and to the control electrode to apply an actuating signal to said control electrode upon the receipt of an incoming signal means for developing a restraining voltage due to undesired signals to oppose the actuating signal, said means for developing a restraining voltage being connected to said signal receiving means and said control electrode and time delay means connected to said relay switching means and to the source of power and switched into and out of circuit by operation of the relay switching means to maintain the relay switching means in actuated condition for a short period of time after actuation independent of the developing and application of restraining voltages.

Y 3. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, signal re ceiving means connected to the source of power and to the control electrode to apply an actuating signal to said control electrode upon the receipt of an incoming signal, a second electronic means connected in parallel with the first electronic means, biasing means for the second electronic means normally biasing it to the cutoff and time delay means connected to the biasing means, the source of power and the relay switching means to change the bias on the second electronic means upon actuation of the relay switching means so that the second electronic means may conduct for a predetermined time.

4. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, signal receiving and amplifying means connected to the source of power for receiving high frequency unmodulated operating waves, frequency selective coupling means connected to the output of the amplifying means, a plurality of rectifying means connected to the frequency selective coupling means, a plurality of resistance means each connected to one of the rectifying means and across which control signals are developed, said resistances being connected together with opposed polarity, one having an actuating voltage developed thcreacross and the other a restraining voltage, means connecting said resistance means to the control electrode so that the resultant voltage controls the electronic means and time delay means connected to the rectifying means developing the restraining voltage and having a discharge period long with respect to the cylic period of modulating Waves to assure that no actuation will take place upon the receipt of modulated carrier waves.

5. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means to control operation of the same, said electronic means having a control electrode, means for receiving radiant energy Waves, frequency selective means connected to the means for receiving radiant energy waves, a first rectifying means connected to said frequency selective means, biasing means connected across said rst rectifying means upon which an actuating voltage is developed upon the appearance of a signal of the frequency of the frequency selective lmeans said biasing means being connected to the control electrode of the electronic means to apply control voltages thereto, a second rectifying and biasing means connected to said frequency selective means and to the first rectifying means and developing a restraining voltage of opposite polarity to the actuating voltage to limit the amplitude of the latter, automatic gain control means connected to the second rectifying means and to the means for receiving radiant waves to adjust the gain thereof and time constant coupling means interconnecting the frequency selective means and the second biasing means said time constant means having a period long as compared with the cyclic period of modulation on a signal carrier wave.

6. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, means for receiving radiant energy waves, frequency selective means connected to the means for receiving radiant energy waves, a iirst rectifying means connected to said frequency selective means, biasing means connected across said first rectifying means upon which an actuating voltage is developed upon the appearance of a signal of the frequency of the frequency selective means said biasing means being connected tothe control electrode of the electronic means to apply control voltage thereto, a second rectifying and biasing means connected to said frequency selective means and to the first rectifying means and developing a restraining voltage of opposite polarity to the actuating voltage to limit the amplitude of the latter, automatic gain control means connected to the second rectifying means and to the means for receiving radiant waves to adjust the gain thereof, time constant coupling means interconnecting the control electrode of the electronic means and the rst named biasing means to apply a cornposite control signal to the control electrode upon receipt of a signal of the proper frequency in the means for receiving radiant energy waves, a shunt circuit around the electronic means including a second electronic means normally biased to be non-conductive, and time constant means connected to the second electronic means, to the source of power and to the relay switching means to change the bias on the second electronic means when the relay switching means is actuated.

7. In control means, a source of electrical power, relay switching means connected to said source for controlling desired apparatus, electronic means connected to control the relay switching means, means for supplying a composite signal to the electronic means to control conduction therethrough, said composite signal consisting of a frequency selective operating signal proportional to the average value of the envelope of the applied signal and a restraining signal of opposite polarity whose value is proportional to the envelope peaks on the applied signal.

8. In control means, a source of electrical power, relay switching means connected to said source for controlling desired apparatus, electronic means connected to control the relay switching means, means for supplying a composite signal to the electronic means to control conduction therethrough, said composite signal consisting of a frequency selective operating signal proportional to the average value of the envelope of the applied signal and restraining signal of opposite polarity whose value is proportional to the envelope peaks on the applied signal in which the restraining voltage is not quite as frequency selective as the operating voltage.

9. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, signal receiving and amplifying means connected to said source of electrical power, frequency selective coupling means connected to said amplifying means and responsive only to a desired operating frequency, a l'rst rectifying means connected to the frequency selective coupling means,

rst resistance means connected to said rst rectifying means and across which an actuating voltage is developed upon receipt of an unmodulated signal of the frequency of the selective coupling means, a second rectifying means connected to said frequency selective coupling means, a second resistance means connected to said second rectifying means and across which a restraining voltage is developed, means for connecting said second resistance means to the first resistance means in opposed polarity relation so that the restraining and actuating voltages will oppose, and adjustable biasing means connected to said second rectifying means to determine the threshold of operation and the point at which the restraining voltage will appear and means connecting said first resistance means to the control electrode of the electronic means to apply the resultant voltage thereacross to the control electrode andcontrol the iiow through said electronic means.

10. In control means, a source of electrical power, relay switching means connected to said source of power for controlling desired apparatus, electronic means connected in circuit with the relay switching means, said electronic means having a control electrode, signal receiving and amplifying means connected to said source of electrical power, frequency selective coupling means connected to said amplifying means and responsive only to a desired operating frequency, a first rectifying means connected to the frequency selective coupling means, first resistance means connected to said first rectifying means and across which an actuating voltage is developed upon receipt of an unmodulated signal of the frequency of the selective coupling means, a second rectifying means connected to said frequency selective coupling means, a second resistance means connected to said second rectifying means and across which a restraining voltage is developed, means for connecting said second resistance means to the rst resistance means in opposed polarity relation so that the restraining and actuating voltages will oppose, a time delay circuit connected to said second rectifying means and having a discharge time longer than the cyclic period of modulating waves on the received carrier so that a higher restraining voltage is developed upon receipt of a modulated carrier wave of a given frequency than the actuating voltage and means connecting said rst resistance means to the control electrode of the electronic means so that the resultant voltage will determine the voltage of the control electrode and the ow through the electronic means.

References Cited in the le of this patent UNITED STATES PATENTS 2,695,977 Hupert Nov. 30, 1954 2,724,074 Welker Nov. 15, 1955 2,739,273 Andrews Mar. 20, 1956 

